Solid state battery having a disordered hydrogenated carbon negative electrode

ABSTRACT

A solid state battery comprising a substrate; at least one multilayered electrochemical cell deposited onto the substrate, each multilayered electrochemical cell comprising: a layer of disordered hydrogenated carbon material negative electrode material capable of electrochemically adsorbing and desorbing lithium ions or both lithium and hydrogen ions during charge and discharge; a layer of positive electrode material capable of electrochemically desorbing and adsorbing lithium ions or both lithium and hydrogen ions during charge and discharge; and a layer of insulating/conducting material disposed between the layer of positive electrode material and the layer of negative electrode material, where the layer of insulating/conducting material is electrically insulating and capable of readily conducting or transporting lithium ions or both lithium and hydrogen ions from the layer positive electrode material to the layer of negative electrode material while the battery is charging and from the layer of negative electrode material to the layer of positive electrode material while the battery is discharging; and an electrically conductive layer deposited a top the last of the at least one multilayered electrochemical cells, the electrically conductive layer providing one battery terminal.

RELATED APPLICATION INFORMATION

This is a Continuation of application Ser. No. 08/562,952 filed Nov. 24,1995, now abandoned, which is a continuation-in-part of Ser. No.08/198,757 filed Feb. 18, 1994, now U.S. Pat. No. 5,512,387, which is acontinuation-in-part of Ser. No. 08/155,059, filed Nov. 19, 1993, nowabandoned.

FIELD OF THE INVENTION

The present invention relates generally to solid state ionic conductorsand more specifically to electrically insulating ionic conductors usefulas solid state electrolyte and thin-film all solid state batteriesemploying these ionic conductors.

BACKGROUND OF THE INVENTION

Rechargeable batteries are used in almost every aspect of daily life. Awide variety of industrial, commercial and consumer applications exist.Larger capacity battery uses include such applications as fork lifts,golf carts, uninterruptable power supplies for protection of electronicdata storage, and even energy storage for power production facilities.When electric vehicles are manufactured in mass, demand for low weight,high charge capacity batteries will be greater than ever before. Indeed,to make mass use of electric vehicles economically feasible, very highspecific capacity may be critically necessary.

In electric vehicles, weight is a significant factor. Because a largecomponent of the total weight of the vehicle is the weight of thebatteries, reducing the weight of the cells is a significantconsideration in designing batteries to power electric vehicles.

The 1998 California Clean Air Act has posed an exceptional challenge onbattery scientists and engineers to develop an improved battery that cansupport the commercialization of electric vehicles (EV). Needless tosay, the law has not changed the reality of battery technology. In over100 years of rechargeable battery usage, two chemistries namely:Pb--PbO₂ (known as lead-acid battery) and Cd--NiOOH (known as Ni--Cdbattery) have dominate with more than 90% of the market. Neither of thetwo are likely to fulfill the utopian goals of powering an electric carthat will match the range, economy, and performance of an internalcombustion engine vehicle. Therefore, battery scientists and engineersare forced to study new battery chemistries.

In addition to industrial, commercial and other large scale uses ofbatteries, there are literally thousands of consumer applications ofrechargeable batteries. A rechargeable electrochemical cell is ideallysuited to serve as a portable power source due to its small size, lightweight, high power capacity and long operating life. A rechargeable cellmay operate as an "install and forget" power source. With the exceptionof periodic charging, such a rechargeable cell typically performswithout attention and rarely becomes the limiting factor in the life ofthe device it powers.

Present rechargeable battery systems can be classified into two groupsthose employing liquid electrolytes and those employing solidelectrolytes. Liquid electrolyte systems have been around for manydecades and are the most well known to the general public. Examples ofliquid electrolyte rechargeable battery systems include lead-acid,nickel cadmium, and the more recent nickel-metal hydride systems.

A more recent advancement is the solid electrolyte rechargeable batterysystems. The solid electrolyte devices have several distinct advantagesover those based on liquid electrolytes. These include (1) thecapability of pressure-packaging or hard encapsulation to yieldextremely rugged assemblies, (2) the extension of the operatingtemperature range since the freezing and/or boiling-off of the liquidphase, which drastically affect the device performance when employingliquid electrolytes are no longer a consideration, (3) solid electrolytedevices are truly leak-proof, (4) they have long shelf life due to theprevention of the corrosion of electrodes and of loss of solvent bydrying out which occur when using liquid electrolytes, (5) solidelectrolytes permit micro-miniaturization, and (6) the do not requireheavy, rigid battery cases which are essentially "dead weight" becausethey provide no additional capacity to the battery but must be includedin the total weight thereof.

All of the above considerations have led to a growing use of solidelectrolytes. Solid state batteries and timers are already availablewhich employ the solid electrolyte as a cylindrical pellet with suitableelectrodes on either side. However, this kind of geometry leads tosomewhat poor solid-solid contacts and these devices tend to have highinternal resistances and polarization losses. These problems have beenovercome by the use of thin films as the electrolytes, since thin filmsdeposited on top of each other have excellent contacts and should alsobe able to withstand shocks, acceleration forces and spin rates withoutundue damage.

In forming such a battery system, a solid ion conductor (i.e. solidelectrolyte) for moving ions within the system is required. A solidelectrolyte is classified by its type of movable ion, such as Li⁺-conductive solid electrolyte, Ag⁺ -conductive solid electrolyte, Cu⁺-conductive solid electrolyte, H⁺ -conductive solid electrolyte, etc. Asolid electrochemical element is constituted by combining one of thesesolid electrolytes with an appropriate electrode material. Several solidelectrolytes are known to exhibit good ionic conductivity, some of whichexist in the form of thin films. Oxide ion conductors such as zirconiaare operated at high temperatures due to their low conductivity atambient temperatures. Chloride ion conductors such as PbCl₂ and BaCl₂have similar temperature restrictions. Silver ion such as AgBr, AgCl,and AgI also show low room temperature ionic conductivity.

Of the thin-film, solid state battery systems, lithium-polymer batterieshave received the most widespread interest. Reports in 1979 thatlithiated poly-ethylene-oxide (PEO) possesses lithium ion conductivityraised the expectations for a solid state battery employing PEO as solidelectrolyte. Indeed, if PEO, or other polymers, were a true solidelectrolyte with practical ionic conductivities and a cationic transfernumber of 1, a stable interface with the lithium electrode and goodcharging uniformity could be realized. The expectations, no doubt, werestimulated by the relative success of the true solid electrolyte "B"Alumina, in the Sodium Sulphur battery.

More recently, several researchers proposed the use of "plasticizedpolymers" to enhance conductivity at room temperature. Although the term"plasticized polymers" is the correct material science terminology forthe materials, they are in effect no different than a battery separatorfilled with organic solvent and electrolyte. In this case, we are backto liquid filled systems with all the old unsolved fundamental problemsand several new ones.

Solid electrolytes consist of solid atomic structures which selectivelyconduct a specific ion through a network of sites in a two or threedimensional matrix. If the activation energy for mobility issufficiently low, the solid electrolyte can serve as both the separatorand electrolyte in a battery. This can allow one to fabricate an allsolid state cell.

An important aspect of such electrolytes is that they selectivelyconduct only one type of ion. If that ion features reversibleelectrochemistry with both the positive and negative electrode of thebattery, and if the solid electrolyte itself is inert to the electrodes,the cell will enjoy a uniform and reversible electrochemistry with nocomposition change and no passivation or side reactions.

While true solid electrolyte lithium conductors would not exhibit theinherent problems of Li-polymer systems described herein below, allpolymer electrolytes reported to date are not true solid electrolytes.The conductivity occurs in an amorphous zone that conducts anions betterthan it conducts lithium ions (the transfer number of lithium is lessthan 0.5). As such, ion concentrations in the electrode surface arevariable and irreversible reactions between the anion and the lithiumelectrodes do occur. The combination of the two effects brings aboutpartial passivation of the lithium surface with non uniform dendriticplating on charge. Additionally, the conductivity of the polymerelectrolyte is too low, typically two to four orders of magnitude lowerthan that of aqueous electrolyte. Also, the electrode area required fora 20 kwh battery is 42 m² for Ni--Cd batteries and is 1610 m² forLi-Polymer batteries. This data clearly conveys that in order to deliveracceptable power levels for EV applications, lithium polymer batterieswill require nearly two orders of magnitude, larger electrode area perampere hour than a higher power density Ni--Cd battery. Given thatelectrode processing is the most expensive component in batteryproduction and that the cost of electrode processing is nearly linearwith electrode area, the cost implications of the design areastonishing.

In addition to cost, safety of Li batteries, particularly liquidelectrolyte systems, is always a problem. The single most importantreason rechargeable lithium batteries have not been successful in themarket place is their poor safety record. Most research groups that haveworked on rechargeable lithium cells have "personally experienced"explosions, and explosions have occurred in the field. The problem canbe diagnosed as follows: 1) lithium plating is dendritic, 2) dendriteseventually short through the separator, 3) shorted cells heat up duringcharging, 4) shorted cells will go into reversal during full batterydischarge, 5) low capacity cells will go into reversal during fullbattery discharge, 6) in reversal, lithium is likely to plate on thecathode which can cause direct chemical reaction between cathodematerial and lithium, 7) processes 3 and 6 can generate enough heat tomelt lithium (165 Centigrade), and 8) molten lithium is an extremelystrong reducing agent which will react with most organic and inorganicmaterials. An explosion could occur depending on: (a) the amount oflithium in the cell, (b) the surface to volume aspect ratio of the cell,(c) the reactivity of the other cell components to lithium, (d) thevapor pressure of the products, and (e) the vent design.

Battery design should be aimed at minimizing the risk of lithium meltdown. Given that it is extremely unlikely that lithium melt down can becompletely avoided in mass usage of large rechargeable lithiumbatteries, it is essential to guarantee non explosion when the melt downdoes occur. Dry polymer electrolyte offers some improvement with regardto exposition when compared to high vapor pressure liquid electrolyte.However, that improvement is counteracted by the need for a very thinseparator. Overall, the likelihood of ensuring explosion free melt downsin large cells and batteries is diminutive.

Cells utilizing polymer electrolytes that contain organic solvents, areas likely to be explosive as cells with standard (polymeric) separatorand liquid electrolytes. In this case, depending on cell design, commonexperience places the explosion threshold in the 0.5 to 5 Ah size range;two orders of magnitude smaller than what is required for an EV battery.It should be noted that a cycled lithium electrode is more prone toexplosion than a fresh uncycled one. While this fact has been known forquire some tine, lithium polymer battery developers have shied away frompublishing safety test data on cycled cells.

In spite of its safety problems, there is a continued interest inlithium batteries because of their purportedly high power density. Thisfeature makes rechargeable lithium batteries attractive. Theoreticalenergy densities of most rechargeable lithium chemistries are two and ahalf to three times higher than that of Pb-Acid and Ni--Cd batteries.Indeed, liquid electrolyte rechargeable lithium batteries could be madeto deliver up to 150 Wh/Kg and 200 Wh/liter. This is about three timeshigher than the practical gravimetric energy density delivered by thebest Ni--Cd batteries and four times higher than the practicalgravimetric energy density delivered by the best Pb-Acid batteries.However, the design of the lithium polymer batteries, driven by the poorconductivity of the polymer electrolyte, is very volume inefficient.Specifically, the separator occupies 30% of the stack volume, carbon isadded to the positive electrode in concentration of up to 30% and thepositive electrode utilization is poor. Thus, the practical energydensity is likely to be considerably lower than of what can be achievedwith liquid electrolyte. Estimated deliverable energy density of lithiumpolymer batteries is 15-20% of the theoretical energy density. Thistranslates to (using 485 Wh/Kg as theoretical maximum) approximately 70to 100 Wh/Kg at best. Most likely, compromises that will have to be madeto improve manufacturability, safety and cycle life beyond the currentlaboratory state-of-the-art technology. This will have the effect toreduce the practical energy density to even below the values proposedabove. The power capability of a battery depends upon the physical andchemical properties of the cell components as well as the cell design.Lithium polymer battery developers are trying to counteract the poorinherent conductivity of the polymer electrolytes by reducing theelectrode and separator thickness. Because practical manufacturingreality is likely to impose increases in the electrolyte thickness fromapproximately 2 to 4 mil, the power deliverable by the cell is likely todrop by 30 to 50%.

An area that requires closer attention is power degradation over life.The main degradation mechanism of the cell involves irreversiblereactions between lithium and electrolyte. This reduces the conductivityof the electrolyte as well as increases the impedance of the Lithiumelectrode due to the formation of passive films; both effects reduce thedeliverable power from the battery. Because the cycle life of thelithium polymer battery is short, significant degradation in power islikely to occur in less than 100 cycles.

Other problems arise from real life usage and requirements placed uponbattery systems. Traction batteries are assembled from a string ofindividual cells connected in series. During both charge and discharge,the same amount of current will pass through all the cells. In practicalmanufacturing and usage, it is impossible to keep all cells at exactlythe same state of charge. This forces a weak cell in a battery to gointo reverse during deep discharge and some cells to go into overchargeduring full charge. For a battery to operate at deep discharge cycles,it is essential that individual cells tolerate reverse or overchargewithout damage or safety implications.

Lithium batteries are very poor in this respect. Over discharge willresult in plating lithium on the positive electrode which can result ina spontaneous chemical reaction with severe safety implications.Overcharge is likely to result in electrolyte degradation that cangenerate some volatile gasses as well as increase cell impedance. Theseproblems are particularly severe for lithium cells because: 1)degradation occurs during cycle life, therefore, even if initialcapacities are matched very closely, it is unreasonable to expect thatthe degradation rate will be identical for all cells, 2) the cells tendto develop soft or hard shorts, thereby making it impossible to maintainthe cells at the same state of charge at all times, and 3) cell capacityis dependent on temperature, therefore cells that are physically coolerdue to their location will deliver less capacity than others. Theseconditions make the likelihood of cell reversal, relatively early in thelife of the battery, very high. Of course, cell reversal is likely toresult in venting and or explosion.

It has been propose to install individual diode protection for all cellswhich could be an expensive, although practical, solution for a portablelow watt-hour battery. The increased cost and reduced reliabilityassociated with this solution makes this very undesirable for an EVbattery. Plus, the inherent lack of overcharge and over dischargecapability eliminates any possibility of ever developing a rechargeablelithium-polymer battery of a bipolar design.

An additional problem with the commercialization of Li-polymer batteriesis their high cost. It is difficult to assess the cost, althoughclearly, processing cost per watt-hour should be much higher than thatof traditional batteries. Raw material costs are clearly higher thanPb-Acid, although, it may be similar to Ni--Cd. The cost of raw materialwill rise due to high purity requirements. There are convincing reasonsto expect that lithium polymer batteries, if ever made commercially,will be considerably more expensive than Ni--Cd batteries consideringthat: 1) primary Li--MnO₂ cells, which are in mass production, are stillmore expensive than Ni--Cd cells, 2) the purity requirements for asecondary cell are much higher than that of a primary cell, and 3) theelectrode area per watt-hour of a lithium polymer secondary battery willbe approximately an order of magnitude larger than that of a primaryLi--MnO₂ battery.

Even more problematic than the cost factor is the low cycle life of thelithium polymer batteries, which is particularly important in EVapplications. Small rechargeable lithium batteries employing organicliquid electrolyte have delivered 100 to 400 cycles in laboratory tests.It is anticipated that lithium polymer electrolyte batteries of the samesize could be made to deliver a comparable number of cycles. However,all the data published to date on lithium polymer batteries was run oncells with a very large amount of excess lithium, therefore, noconclusion can be drawn at this stage.

The cycle life of a large multi cell battery is likely to beconsiderably lower than that of a small two-cell battery. Additionalreduction of the expected cycle life results from consideration of thefact that the battery will be limited by the weakest cell, and aspreviously mentioned, the likelihood of temperature or electricalimbalance is high. Further, power may degrade faster than capacity, socycle life could become limited due to an unacceptable drop in power.Therefore, it is probably a fair assumption that if a full size batterywas built at today's state-of-the-art technology, it could possibly make100 cycles or so, which is about an order of magnitude short of what isrequired for an EV.

Therefore, since lithium-polymer batteries will be inadequate to meettoday's requirements for a universally acceptable, thin-film, solidstate rechargeable secondary battery system, other solid state systemsneed to be developed. The solid state battery systems of the presentinvention meet the requirements discussed hereinabove and providegravimetric and volumetric energy densities of unparalleled performance.

SUMMARY OF THE INVENTION

There is disclosed herein a thin film, solid state battery. The batteryincludes a substrate material layer which provides support for thebattery and at least one multilayered electrochemical cell depositedonto the substrate. Each cell of the battery includes a layer ofnegative electrode material, the negative electrode material beingcapable of electrochemically adsorbing and desorbing ions during chargeand discharge thereof, respectively. The multilayered electrochemicalcell additionally contains a layer of positive electrode material, thepositive electrode material being capable of electrochemically desorbingand adsorbing ions during charge and discharge thereof respectively.Finally the multilayered electrochemical cell contains a layer ofinsulating/conducting material disposed between the layer of positiveelectrode material and the layer of negative electrode material. Theinsulating/conducting material is electrically insulating and capable ofreadily conducting or transporting ions from the positive electrode tothe negative electrode while the battery is charging and from thenegative electrode to the positive electrode while the battery isdischarging. That battery additionally includes an electricallyconductive layer deposited on top of the last of said at least onemultilayered electrochemical cells. The electrically conductive materialacts as a top battery terminal.

In preferred embodiments, the positive electrode layer includes lithiumnickelate or amorphous vanadium oxide and the negative electrodematerial includes disordered hydrogenated carbon or lithium metal. Inanother preferred embodiment, one electrode provides a source of lithiumions, while the other provides a source of hydrogen ions. The solidstate lithium or lithium/proton conducting material includes a lithiatedor lithiated/hydrogenated electrical insulator material, which may be alithiated or lithiated/hydrogenated silicon nitride material. Thelithiated silicon nitride material preferably has an atomic ratio ofbetween about 20% and about 50% lithium, between about 20% and about 40%silicon and about 20% to about 50% nitrogen while thelithiated/hydrogenated silicon nitride material preferably has an atomicratio of between about 10 to 40 atomic % lithium, about 10 to 40 atomic% hydrogen, about 20 to 40 atomic % silicon, and about 20 to 50 atomic %nitrogen. Preferably the substrate material is formed from anelectrically conductive material and acts as one of the electricalterminal of the battery. However, the substrate material may beelectrically insulating with an electrically conductive materialdeposited on it. The deposited electrically conductive material acts asthe one of the battery terminals. When the battery includes more thanone multi-layered cell, current collector material layers are depositedbetween the positive electrode of one cell and the negative electrode ofthe adjacent cell. Typically, the electrically conductive batteryterminals and the current collector material layers are formed fromnon-reactive metals such as molybdenum or aluminum.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional depiction of a first embodiment of the solidstate battery of the instant invention specifically illustrating theindividual layers thereof;

FIG. 2 is a cross-sectional depiction of a second embodiment of thesolid state battery of the instant invention specifically illustratingthe individual layers thereof, including plural electrochemical cellsand current collectors therebetween.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a cross-sectional depiction of a thin-film solid state batteryof the present invention. Specifically, reference numeral 1 is thesubstrate of the thin-film battery. The substrate provides support forthe battery and may also serve as the bottom electrical terminal of thebattery. Substrate 1 may be formed from an electrically conductive metalsuch as aluminum, nickel, copper or stainless steel, or it may be formedfrom a light weight, electrically insulating polymer or ceramicmaterial. If the substrate 1 is formed of an electrically insulatingmaterial or is reactive with the battery electrode materials, then anelectrically conductive bottom battery terminal layer 2 is depositedonto the substrate. The material used to form the battery terminal layer2 may be an electrically conductive metal such as aluminum, nickel orcopper, or may even be an electrically conductive ceramic or oxidematerial. For maximum weight savings, the substrate 1 plus any batteryterminal layer 2 should be only as thick as needed to perform theirsupport and conduction functions. Any additional thickness will onlyincrease the "dead weight" of the battery. Typically the total thicknessof the substrate 1 plus the battery terminal layer 2 will not be greaterthan about 200 microns and preferably not greater than about 50 to 100microns. The battery terminal layer 2 is preferably between 0.5 and 5microns thick. Deposited on top of the substrate 1 and battery terminallayer 2 is at least one multi-layered electrochemical cell. Eachelectrochemical cell includes a thin-film negative electrode layer 3, athin-film positive electrode layer 5 and a thin-film solid electrolyteproton conductive layer 4.

The thin-film negative electrode layer 3 is typically between about 1and 15 microns thick and is formed from a material whichelectrochemically adsorbs and desorbs ions such as ionic hydrogen duringcharging and discharging thereof, respectively. Typically the layer isformed from electrochemical hydrogen storage materials such as metalhydride materials. These metal hydride material may be any of thosealready known any used in liquid electrolyte nickel-metal hydridebatteries. These materials may be AB₂ or AB₅ type metal hydridematerials. They may be amorphous, polycrystalline, microcrystalline,nanocrystalline, single crystal or multi-structural materials. They mayinclude only a single compositional phase or may include multiplecompositional phases. An extensive review of the known metal hydridematerials useful in electrochemical cells is given in U.S. Pat. No.5,096,667, the disclosure of which is incorporated herein by reference.

In addition to the known metal hydride materials, new metal hydridesystems can be developed to take advantage of the environmentaldifferences between an alkaline liquid electrolyte system and the newthin-film solid electrolyte systems. For example, in a liquidelectrolyte system, there is generally a problem with corrosion of theelectrode due to the caustic nature of the alkaline electrolyte.Therefore, elements which provide corrosion resistance must be added tothe negative electrode material to mitigate corrosion damage. In thesolid electrolyte system of the present invention, no such corrosionproblems will occur due to the absence of caustic liquids and as such,no corrosion inhibitor materials will need to be added to the negativeelectrode.

Alternatively, in the case of lithium systems, metallic lithium orlithium intercalated disordered hydrogenated carbon can be used as thenegative electrode layer 3.

The positive electrode layer 5 is typically between 5 and 20 micronsthick and is formed from a material which electrochemically desorbs andadsorbs ions such as ionic hydrogen during charging and dischargingthereof, respectively. Typically the layer is formed from a transitionmetal hydroxide such as nickel hydroxide material. The nickel hydroxidematerial can be any of those material known in the prior art for use inrechargeable battery systems. They may also be advanced active materialslike the locally ordered, disordered, high capacity, long cycle lifepositive electrode material disclosed in U.S. patent application Ser.No. 7/975,031 filed Nov. 12, 1992 and Ser. No. 8/027,973 filed Mar. 8,1993, the disclosures of which are incorporated herein by reference.These materials include a solid solution nickel hydroxide electrodematerial having a multiphase structure and at least one compositionalmodifier to promote said multiphase structure. The multiphase structurecomprises at least one polycrystalline y-phase including apolycrystalline γ-phase unit cell comprising spacedly disposed plateswith at least one ion incorporated around the plates, the plates havinga range of stable intersheet distances corresponding to a 2⁺ oxidationstate and a 3.5⁺, or greater, oxidation state. The compositionalmodifier is a metal, a metallic oxide, a metallic oxide alloy, a metalhydride, and/or a metal hydride alloy. Preferably the compositionalmodifier is chosen from the group consisting of Al, Bi, Co, Cr, Cu, Fe,In, LaH₃, Mn, Ru, Sb, Sn, TiH₂, TiO, Zn and mixtures thereof. Morepreferably, at least three of these compositional modifiers are used.The at least one chemical modifier incorporated is preferably chosenfrom the group consisting of Al, Ba, Ca, Co, Cr, Cu, F, Fe, K, Li, Mg,Mn, Na, Sr, and Zn.

Also, for lithium ion systems, the positive electrode layer 5 can beformed from a material such as lithium nickelate (LiNiO₄), lithiumcobaltate or (LiCoO₄) lithium manganate (LiMnO₄), vanadium oxide,titanium disulfide, etc.

Between the negative electrode layer 3 and the positive electrode layer5, is deposited a thin-film solid state electrolyte layer 4. This layeris typically between about 0.5 and 2 microns thick, but may be as thinas 1000 Angstroms if the layer onto which it is deposited has a lowdegree of surface roughness. The type of ionic conductivity required ofthe solid electrolyte is dependent on the electrochemical reactionsinvolved in the cell. Since the charging cycle electrode reactions ofthe instant rechargeable protonic battery are:

    M+H.sup.+ e.sup.- -CHARGE>MH; and

    Ni(OH).sub.2 -CHARGE>NiOOH+H.sup.+ e.sup.-,

the solid state electrolyte layer 4 which separates the positiveelectrode layer 5 and the negative electrode layer 3 must be a protonconductor. That is, the solid electrolyte material must be capable ofreadily conducting or transporting protons from the positive electrodelayer 5 to the negative electrode layer 3 while the battery is chargingand from the negative electrode layer 3 to the positive electrode layer5 while the battery is discharging. The solid electrolyte layer 4 mustalso be electrically insulating so that the battery electrodes do notshort. That is, the electrolyte also acts as the electrode separator.The present inventors have found that a lithiated,lithiated/hydrogenated or hydrogenated electrical insulator has all ofthe characteristics required depending upon the ion(s) to betransported. Typically this is a lithiated and/or hydrogenated siliconnitride material, but lithiated and/or hydrogenated silicon oxide orlithiated and/or hydrogenated silicon oxynitride may also be used.Preferably the hydrogenated silicon nitride material has a composition,in atomic percent, of between about 20% and about 50% hydrogen, betweenabout 20% and about 40% silicon and about 20% to about 50% nitrogen. Theratio of silicon to nitrogen is generally between about 2:1 and about1:2, but may be varied outside this range if specifically advantageousunder the circumstances.

Alternatively, for the lithium systems, the charging electrode reactionsare:

    C+Li.sup.+ +e.sup.- -CHARGE>LiC; and

    LiNiO.sub.2 -CHARGE>NiO.sub.2 +Li.sup.+ +e.sup.-,

therefore, in the lithium systems, a lithium conductor is needed. Solidlithium conductors useful as the ionic conductor layer 4 are lithiatedsilicon nitride (Li₈ SiN₄), lithium phosphate (LiPO₄), lithium titaniumphosphate (LiTiPO₄) and lithium phosphonitride (LiPO_(4-x) N_(x) where0<x<1).

A top battery terminal layer 6 is deposited on top of the positiveelectrode layer 5. The battery terminal layer 6 is typically between 1and 5 microns thick and is formed from an electrically conductivematerial such as a metal or an electrically conductive ceramic or oxide.Specifically, aluminum, copper or nickel may be used.

Turning now to FIG. 2 there is depicted therein a solid state battery ofthe instant invention containing multiple stacked electrochemical cells.The reference numeral of the layers of this battery correspond to thoseof the battery depicted in FIG. 1. Additionally, because this batteryincludes more than one electrochemical cell, a layer of currentcollecting material 7 is deposited between positive electrode layer 5 orone cell and the negative electrode layer 3 of the adjacent cell. Thislayer is formed of an electrically conductive material and is typicallybetween 1000 angstroms and 0.5 microns thick. Preferably this layer isformed from a metal such as aluminum, copper or nickel and is resistantto the conduction of protons.

EXAMPLE 1

A one square meter multiple cell thin-film solid state battery of thetype depicted in FIG. 2 having 10 cells will serve as an example of theefficacy of the present design. Each cell contains a positive electrodelayer 5 which is formed from conventional nickel hydroxide and is about10 microns thick. Each cell also contains a negative electrode layer 3of metal hydride material and is about 4 microns thick. Finally eachcell contains a solid state electrolyte layer 4 formed from hydrogenatedsilicon nitride material and is about 2 microns thick. Between the cellsare current collector layers 7 which are formed of aluminum and areabout 0.5 microns thick. The cells are deposited onto an aluminumsubstrate 1 which also serves as the bottom battery terminal 2. Thesubstrate 1 is about 100 microns thick. On top of the positive electrodelayer 5 of the final cell is deposited a top battery terminal layer 6which is formed of aluminum and is about 5 microns thick.

This battery would have a Specific Capacity calculated as follows:

1) Basis 1 m², 1 e⁻ transfer; 10 positive electrode layers formed fromNi(OH)₂

2) Density of Ni(OH)₂ =3.95 g/cm³

3) Total volume of 10 Ni(OH)₂ layers=10*(1 m)*(1 m)*(10×10⁻⁶ m)=1×10⁻⁴m³ or 100 cm³

4) Total weight of 10 Ni(OH)₂ layers=(3.95 g/cm³)*(100 cm³)=395 gNi(OH)₂

5) Charge capacity of Ni(OH)₂ =289 mAh/g

6) Total capacity of 10 Ni(OH)₂ layers=(289 mAh/g)*(395 g)=114115mAh=114.1 Ah

7) Charge capacity of metal hydride material=400 mAh/g

8) Weight of metal hydride needed to equal 114.1 Ah=(114.1 ah)*(1g/0.400 Ah)=285 g

9) Volume of substrate=(1 m)*(1 m)*(100×10⁻⁶ m)=1×10⁻⁴ m³ =100 cm³

10) Weight of substrate=(2.7 g/cm³)*(100 cm³)=270 g

11) Total volume of 10 hydrogenated silicon nitride layers=10*(1 m)*(1m)*(2×10⁻⁶)=2×10⁻⁵ m³ =20 cm³

12) Total weight of 10 hydrogenated silicon nitride layers=(1.7g/cm³)*(20 cm³)=34 g

13) Total volume of 9 current collector layers=9*(1 m)*(1 m)*(0.5×10⁻⁶cm)=4.5×10⁻⁶ m³ =4.5 cm³

14) Total weight of 9 current collector layers=(2.7 g/cm³)*(4.5cm³)=12.15 g

15) Volume of top battery terminal=(1 m)*(1 m)*(5×10⁻⁶ m)=5×10⁻⁶ m³ =5cm³

16) Weight of top battery terminal=(2.7 g/cm³)*(5 cm³)=13.5 g

17) Total battery weight=(395 g)+(285 g)+(270 g)+(34 g)+(12.15 g)+(13.5g)=1009.65 g=1.01 Kg

18) Specific capacity is (114.155 Ah)/(1.00965 Kg)=113.1 Ah/Kg

19) Energy density is (1.4 V)*(113.1 Ah/Kg)=158.34 Wh/Kg

20) Volume of battery=(1 m)*(1 m)*(250×10⁻⁶ m)=2.5×10⁻⁴ m³ =0.25 l

21) Volumetric energy density is (114.155 Ah)*(1.4 V)/(0.25 l)=639.3Wh/l

EXAMPLE 2

Another example of the solid state battery having the same structure anddimensions as that in Example 1, but using advanced nickel hydroxideactive materials and assuming about 1.7 electron transfer give aspecific capacity as calculated below.

1) Basis 1 m², 1.7 e⁻ transfer; 10 positive electrode layers formed fromadvanced Ni(OH)₂ material

2) Density of Ni(OH)₂ =3.95 g/cm³

3) Total volume of 10 Ni(OH)₂ layers=10*(1 m)*(1 m)*(10×10⁻⁶ m)=1×10⁻⁴m³ or 100 cm³

4) Total weight of 10 Ni(OH)₂ layers=(3.95 g/cm³)*(100 cm³)=395 gNi(OH)₂

5) Charge capacity of Ni(OH)₂ =483 mAh/g

6) Total capacity of 10 Ni(OH)₂ layers=(483 mAh/g)*(395 g)=190785mAh=190.8 Ah

7) Charge capacity of metal hydride material=400 mAh/g

8) Weight of metal hydride needed to equal 190.8 Ah=(190.8 ah)*(1g/0.400 Ah)=477 g

9) Volume of substrate=(1 m)*(1 m)*(100×10⁻⁶ m)=1×10⁻⁴ m³ =100 cm³

10) Weight of substrate=(2.7 g/cm³)*(100 cm³)=270 g

11) Total volume of 10 hydrogenated silicon nitride layers=10*(1 m)*(1m)*(2×10⁻⁶)=2×10⁻⁵ m³ =20 cm³

12) Total weight of 10 hydrogenated silicon nitride layers=(1.7g/cm³)*(20 cm³)=34 g

13) Total volume of 9 current collector layers=9*(1 m)*(1 m)*(0.5×10⁻⁶m)=4.5×10⁻⁶ m³ =4.5 cm³

14) Total weight of 9 current collector layers=(2.7 g/cm³)*(4.5cm³)=12.15 g

15) Volume of top battery terminal=(1 m)*(1 m)*(5×10⁻⁶ m)=5×10⁻⁶ m³ =5cm³

16) Weight of top battery terminal=(2.7 g/cm³)*(5 cm³)=13.5 g

17) Total battery weight=(395 g)+(477 g)+(270 g)+(34 g)+(12.15 g)+(13.5g)=1201.65 g=1.20165 Kg

18) Specific capacity is (190.785 Ah)/(1.20165 Kg)=158.8 Ah/Kg

19) Gravimetric energy density is (1.4 V)*(158.8 Ah/Kg)=222.32 Wh/Kg

20) Volume of battery=(1 m)*(1 m)*(250×10⁻⁶ m)=2.5×10⁻⁴ m³ =0.25 l

21) Volumetric energy density is (190.785 Ah)*(1.4 V)/(0.25 l)=1068.4Wh/l

EXAMPLE 3

Next, a battery similar to that disclosed in Example 1 except that theprotonic system was substituted by a lithium system is presented. Eachof the 10 cells contains a positive electrode layer 5 which is formedfrom lithium nickelate (LiNiO₂) and is about 10 microns thick. Each cellalso contains a negative electrode layer 3 of disordered hydrogenatedcarbon material and is about 4 microns thick. Finally each cell containsa solid state electrolyte layer 4 formed from lithiated silicon nitridematerial and is about 2 microns thick. Between the cells are currentcollector layers 7 which are formed of aluminum and are about 0.5microns thick. The cells are deposited onto an aluminum substrate 1which also serves as the bottom battery terminal 2. The substrate 1 isabout 100 microns thick. On top of the positive electrode layer 5 of thefinal cell is deposited a top battery terminal layer 6 which is formedof aluminum and is about 5 microns thick.

This battery would have a Specific Capacity calculated as follows:

1) Basis 1 m², 1 e⁻ transfer; 10 positive electrode layers formed fromLiNiO₂

2) Density of LiNiO₂ =4.78 g/cm³

3) Total volume of 10 LiNiO₂ layers=10*(1 m)*(1 m)*(10×10⁻⁶ m)=1×10⁻⁴ m³or 100 cm³

4) Total weight of 10 LiNiO₂ layers=(4.78 g/cm³)*(100 cm³)=478 g LiNiO₂

5) Charge capacity of LiNiO₂ =275 mAh/g

6) Total capacity of 10 LiNiO₂ layers=(275 mAh/g)*(478 g)=131450mAh=131.5 Ah

7) Charge capacity of disordered hydrogenated carbon intercalationmaterial=370 mAh/g

8) Weight of carbon needed to equal 131.5 Ah=(131.5 Ah)*(1 g/0.37Ah)=355.3 g

9) Volume of substrate=(1 m)*(1 m)*(100×10⁻⁶ m)=1×10⁻⁴ m³ =100 cm³

10) Weight of substrate=(2.7 g/cm3)*(100 cm³)=270 g

11) Total volume of 10 lithiated silicon nitride layers=10*(1 m)*(1m)*(2×10⁻⁶)=2×10⁻⁵ m³ =20 cm³

12) Total weight of 10 lithiated silicon nitride layers=(1.7 g/cm³)*(20cm³)=34 g

13) Total volume of 9 current collector layers=9*(1 m)*(1 m)*(0.5×10⁻⁶m)=4.5×10⁻⁶ m³ =4.5 cm³

14) Total weight of 9 current collector layers=(2.7 g/cm³)*(4.5cm³)=12.15 g

15) Volume of top battery terminal=(1 m)*(1 m)*(5×10⁻⁶ m)=5×10⁻⁶ m³ =5cm³

16) Weight of top battery terminal=(2.7 g/cm³)*(5 cm³)=13.5 g

17) Total battery weight=(478 g)+(355.3 g)+(270 g)+(34 g)+(12.15g)+(13.5 g)=1162.95 g=1.16 Kg

18) Specific capacity is (131.450 Ah)/(1.16 Kg)=113.0 Ah/Kg

19) Energy density is (3.8 V)*(113.0 Ah/Kg)=429.5 Wh/Kg

20) Volume of battery=(1 m)*(1 m)*(250×10⁻⁶ m)=2.5×10⁻⁴ m³ =0.25 l

21) Volumetric energy density is (131.450 Ah)*(3.8 V)/(0.25 l)=1998.04Wh/l

EXAMPLE 4

Another lithium system battery uses amorphous vanadium oxide as thepositive electrode material and lithium metal as the negative electrode.That is, each of the 10 cells contains a positive electrode layer 5which is formed from amorphous vanadium oxide (a-V₂ O₅) and is about 10microns thick. Each cell also contains a negative electrode layer 3 oflithium metal which is about 19 microns thick. Finally each cellcontains a solid state electrolyte layer 4 formed from lithiated siliconnitride material and is about 2 microns thick. The composition of thelithiated silicon nitride film is typically about 20 to 50 atomic %lithium, about 20 to 40 atomic % silicon, and about 20 to 50 atomic %nitrogen. Between the cells are current collector layers 7 which areformed of molybdenum and are about 0.5 microns thick. The cells aredeposited onto an aluminum or nickel substrate 1 which also serves asthe bottom battery terminal 2. The substrate 1 is about 50 to 100microns thick. On top of the positive electrode layer 5 of the finalcell is deposited a top terminal layer 6 which is formed of aluminum ormolybdenum and is about 5 microns thick.

This battery would have a Specific Capacity calculated as follows:

1) Basis 1 m², 1 e⁻ transfer; 10 positive electrode layers formed froma-V₂ O₅

2) Density of a-V₂ O₅ =3.3 g/cm³

3) Total volume of 10 a-V₂ O₅ layers=10*(1 m)*(1 m)*(10×10⁻⁶ m)=1×10⁻⁴m³ or 100 cm³

4) Total weight of 10 a-V₂ O₅ layers=(3.3 g/cm³)*(100 cm³)=330 g

5) Charge capacity of a-V₂ O₅ =364 mAh/g

6) Total capacity of 10 a-V₂ O₅ layers=(364 mAh/g)*(330 g)=120000mAh=120 Ah

7) Volume of lithium 10*(1 m)*(1 m)*(19×10⁻⁶ m)=1.9×10⁻⁴ m³ or 190 cm³

8) Total weight of 10 lithium layers=0.53 g/cm³ * 190 cm³ =100.7 g

9) Volume of substrate=(1 m)*(1 m)*(100×10⁻⁶ m)=1×10⁻⁴ m³ =100 cm³

10) Weight of substrate=(2.7 g/cm³)*(100 cm³)=270 g

11) Total volume of 10 lithiated silicon nitride layers=10*(1 m)*(1m)*(2×10⁻⁶)=2×10⁻⁵ m³ =20 cm³

12) Total weight of 10 lithiated silicon nitride layers=(1.7 g/cm³)*(20cm³)=34 g

13) Total volume of 9 current collector layers=9*(1 m)*(1 m)*(0.5×10⁻⁶m)=4.5×10⁻⁴ m³ =4.5 cm³

14) Total weight of 9 current collector layers=(10.2 g/cm³)*(4.5cm³)=45.9 g

15) Volume of top battery terminal=(1 m)*(1 m)*(5×10⁻⁶ m)=5×10⁻⁶ m³ =5cm³

16) Weight of top battery terminal=(2.7 g/cm³)*(5 cm³)=13.5 g

17) Total battery weight=(330 g)+(100.7 g)+(270 g)+(34 g)+(45.9 g)+(13.5g)=794.1 g=0.794 Kg

18) Specific capacity is (120 Ah)/(0.794 Kg)=151.1 Ah/Kg

19) Energy density is (3.5 V)*(151.1 Ah/Kg)=528.9 Wh/Kg

20) Volume of battery=(1 m)*(1 m)*(400×10⁻⁶ m)=4×10⁻⁴ m³ =0.4 l

21) Volumetric energy density is (120 Ah)*(3.5 V)/(0.4 l)=1050 Wh/l

EXAMPLE 5

Finally, a battery combining both protons and lithium ion transfer ispresented. Each of the 10 cells contain a positive electrode layer 5which is formed from lithium nickelate (LiNiO₂) (which can be partiallyor totally substituted by LiCoO₂ or LiMnO₂) and is about 10 micronsthick. Each cell also contains a negative electrode layer 3 ofhydrogenated carbon material and is about 4 microns thick. Finally eachcell contains a solid state electrolyte layer 4 formed fromlithiated/hydrogenated silicon nitride material and is about 2 micronsthick. The composition of the lithiated/hydrogenated silicon nitride istypically about 10 to 40 atomic % lithium, about 10 to 40 atomic %hydrogen, about 20 to 40 atomic % silicon, and about 20 to 50 atomic %nitrogen. Between the cells are current collector layers 7 which areformed of aluminum or nickel and are about 0.5 microns thick. The cellsare deposited onto an aluminum or nickel substrate 1 which also servesas the bottom battery terminal 2. The substrate 1 is about 100 micronsthick. On top of the positive electrode layer 5 of the final cell isdeposited a top terminal layer 6 which is formed of aluminum or nickeland is about 5 microns thick. The energy density of this battery shouldbe a combination of the lithium and hydrogen densities. The battery willexhibit multiple charge/discharge plateau voltages corresponding to bothlithium and hydrogen cell potentials. This will allow for longerdischarge times and increased cell capacity.

This battery can be thought of as a half-charged battery. That is,initially the positive electrode is LiNiO₂ and the negative electrode ishydrogenated carbon. The "as deposited" cell is in a half charged state.During formation (i.e. full charging) hydrogen ions are transferred tothe lithium nickelate material according to the following reactions.

    LiNiO.sub.2 +H.sup.+ +e.sup.- >HLiNiO.sub.2 ; and

    CH.sub.x ->C+xH.sup.+ +xe.sup.-

The subsequent discharge reactions (i.e. full discharge) are as follows.

    HLiNiO.sub.2 ->NiO.sub.2 +H.sup.+ +Li.sup.+ +2e.sup.- ; and

    C+xH.sup.+ +yLi.sup.+ +(x+y)e.sup.- >CH.sub.x Li.sub.y

Therefore, it can clearly be seen that the solid state batteries of thepresent invention show tremendous promise for commercial, industrial andconsumer uses. Particularly, with regard to the gravimetric andvolumetric energy densities shown above, application of these batteriesto electric vehicle would be highly advantageous.

It is to be understood that the disclosure set forth herein is presentedin the form of detailed embodiments described for the purpose of makinga full and complete disclosure of the present invention, and that suchdetails are not to be interpreted as limiting the true scope of thisinvention as set forth and defined in the appended claims.

We claim:
 1. A solid state battery comprising:A.) a substrate; B.) atleast one multilayered electrochemical cell deposited onto saidsubstrate, each multilayered electrochemical cell comprising:1.) a layerof disordered hydrogenated carbon negative electrode material capable ofelectrochemically adsorbing and desorbing lithium ions during charge anddischarge; 2.) a layer of positive electrode material capable ofelectrochemically desorbing and adsorbing lithium ions during charge anddischarge; and 3.) a layer of lithiated silicon nitride materialdisposed between said layer of positive electrode material and saidlayer of negative electrode material, where said layer of lithiatedsilicon nitride material is electrically insulating and capable ofreadily conducting or transporting lithium ions from said layer ofpositive electrode material to said layer of negative electrode materialwhile said battery is charging and from said layer of negative electrodematerial to said layer of positive electrode material while said batteryis discharging; and C.) an electrically conductive layer deposited a topthe last of said at least one multilayered electrochemical cells, saidelectrically conductive layer providing one battery terminal.
 2. Thesolid state battery of claim 1, wherein said layer of negative electrodematerial, said layer of positive electrode material, and said layer ofinsulating/conducting material are all thin film materials.
 3. The solidstate battery of claim 1, wherein said layer of positive electrodematerial comprises a layer of amorphous V₂ O₅.
 4. The solid statebattery of claim 1, wherein said lithiated silicon nitride materialcomprises: about 20 to 50 atomic % lithium, about 20 to 40 atomic %silicon, and about 20 to 50 atomic % nitrogen.
 5. The solid statebattery of claim 1, wherein said substrate is electrically conductiveand acts as a second electrical terminal of said battery.
 6. The solidstate battery of claim 1, wherein said substrate is electricallyinsulative and an electrically conductive material layer is depositedonto said substrate, said electrically conductive material layer actingas a second battery terminal.
 7. The solid state battery of claim 1,including more than one of said multilayered electrochemical cells andfurther comprising current collector material layers deposited betweensaid layer of positive electrode material of one multilayeredelectrochemical cell and said layer of negative electrode material of anadjacent electrochemical cell.
 8. A solid state battery comprising:asubstrate; at least one multilayered electrochemical cell deposited ontosaid substrate, each layer of said multilayered electrochemical cellcomprising:a layer of disordered hydrogenated carbon negative electrodematerial capable of electrochemically adsorbing and desorbing bothprotons and lithium ions during charge and discharge; a layer ofpositive electrode material capable of electrochemically desorbing andadsorbing both protons and lithium ions during charge and discharge; anda layer of insulating/conducting material disposed between said layer ofpositive electrode material and said layer of negative electrodematerial, where said layer of insulating/conducting material iselectrically insulating and capable of readily conducting ortransporting both protons and lithium ions from said layer of positiveelectrode material to said layer of negative electrode material whilesaid battery is charging and from said layer of negative electrodematerial to said layer of positive electrode material while said batteryis discharging; and an electrically conductive layer deposited a top thelast of said at least one multilayered electrochemical cells, saidelectrically conductive layer providing one battery terminal.
 9. Thesolid state battery of claim 8, wherein said layer of negative electrodematerial, said layer of positive electrode material, and said layer ofinsulating/conducting material are all thin film materials.
 10. Thesolid state battery of claim 8, wherein said layer of positive electrodematerial comprises a layer of at least one of LiNiO₂, LiCoO₂, or LiMnO₂.11. The solid state battery of claim 8, wherein said layer ofinsulating/conducting material includes a lithiated/hydrogenatedelectrically insulating material.
 12. The solid state battery of claim8, wherein said insulating/conducting material is selected from thegroup consisting of a lithiated/hydrogenated silicon nitride material, alithiated/hydrogenated silicon oxide and a lithiated/hydrogenatedsilicon oxynitride.
 13. The solid state battery of claim 12, whereinsaid insulating/conducting material includes a lithiated/hydrogenatedsilicon nitride material.
 14. The solid state battery of claim 13,wherein said insulating/conducting material is a lithiated/hydrogenatedsilicon nitride film comprising: about 10 to 40 atomic % lithium, about10 to 40 atomic % hydrogen, about 20 to 40 atomic % silicon, and about20 to 50 atomic % nitrogen.
 15. The solid state battery of claim 8,wherein said substrate is electrically conductive and acts as a secondelectrical terminal of said battery.
 16. The solid state battery ofclaim 8, wherein said substrate is electrically insulative and anelectrically conductive material layer is deposited onto said substrate,said electrically conductive material layer acting as a second batteryterminal.
 17. The solid state battery of claim 8, including more thanone of said multilayered electrochemical cells and further comprisingcurrent collector material layers deposited between said layer ofpositive electrode material of one multilayered electrochemical cell andsaid layer of negative electrode material of an adjacent multilayeredelectrochemical cell.